Lead-acid deep cycle batteries ​last the longest with best capacity if they are never cycled more than 50% [[electrical:​depth_of_discharge|Depth of Discharge]]((and fully charged afterwards)). ​ That point is somewhere around 12.20v when rested or very lightly loaded. ​

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Lead-acid deep cycle batteries are typically discharged ​50% [[electrical:​depth_of_discharge|Depth of Discharge]] ​or less ((and fully charged afterwards)). ​ That point is somewhere around 12.20v when rested or very lightly loaded. ​

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This following chart((http://​www.trojanbattery.com/​pdf/​GEL_Trojan_ProductLineSheet.pdf)) shows DoD vs expected duty cycles. ​ In an offgrid scenario we will assume the bank is cycled every night. ​ If the bank is drained to the usual 50% DoD the bank((under lab conditions)) is predicted to last 1000 cycles, or about 3 years. ​ If the bank cycle is shallower to 20% DoD the bank is expected to last 2500 cycles, or about 7.5 years. ​ If the bank is deeply cycled to 80% DoD the bank is expected to last 500 cycles, or about 1.5 years.

This following chart((http://​www.trojanbattery.com/​pdf/​GEL_Trojan_ProductLineSheet.pdf)) shows DoD vs expected duty cycles. ​ In an offgrid scenario we will assume the bank is cycled every night. ​ If the bank is drained to the usual 50% DoD the bank((under lab conditions)) is predicted to last 1000 cycles, or about 3 years. ​ If the bank cycle is shallower to 20% DoD the bank is expected to last 2500 cycles, or about 7.5 years. ​ If the bank is deeply cycled to 80% DoD the bank is expected to last 500 cycles, or about 1.5 years.